Lennox XC21 Installation Instructions Manual page 47

A simple test can be used to test the fan motor operation. A fully charged 9V battery will be required for this procedure.
B4 FAN MOTOR TEST
This is a test that will verify that the motor does operate.
1. Verify main (240 volt) power if OFF to unit.
2. Remove both wires (brown and black) from the J2 terminal on the A177 fan
motor control.
3. Room thermostat should be in OFF position (unit in idle mode − no heating or
cooling demands)
4. Turn main power (240 volt) ON to unit.
5. Connect 9 Volt battery to B4 fan motor plugs as noted in picture
below.
6. B4 fan motor should run at a reduced fan speed.
7. If B4 fan motor does not run, then replace fan motor assembly.
REMOVE BOTH LEADS
FROM J2 TERMINALS
BLACK LEAD
BROWN LEAD
B4 Fan Motor Test Procedure
A177 FAN MOTOR CONTROL
J2
CONNECT B4 FAN MOTOR BLACK
COMMON WIRE TO 9V BATTERY
Figure 26. B4 Fan Motor Test
BLACK LEAD
J2
BROWN LEAD
BLACK LEAD
NEGATIVE TERMINAL
NEGATIVE TERMINAL
FULLY CHARGED 9V BATTERY
Page 47
BROWN LEAD
CONNECT B4 FAN MOTOR WIRE
TO 9V BATTERY POSITIVE
V
TERMINAL
POSITIVE TERMINAL
XC21 SERIES